Can is a modal with multiple uses including: ability, permission, request, offer, suggestion, possibility
Ability: We can speak Spanish
Permission: My mom said I can go out on Friday night
Request: Can you pick up some milk on your way home?
Offer: I can bake Linda’s birthday cake if you don’t have time.
Suggestion: We can go to the amusement park next weekend
Possibility: Exams can be really stressful
May can be used to express possibility, permission
Possibility: I may go out tonight
Permission: You may proceed to the front gate
Must/Mustn’t used to express obligation
Obligation: You must study for the biology exam.
Should/Shouldn’t used for advice and obligation
Advice: You should wear a warm jacket, it’s really cold out
Obligation: You should call your mother
Would used for requests and habits
Request: Would you be able to work on Saturday?
Habits (past): I would usually go dancing on Wednesdays
Could used for ability, polite request, offer, suggestion, possibility
Ability: I could ride a unicycle when I was a kid.
Polite request: Could I have a glass of wine, please?
Offer: Could I interest you in a glass of wine?
Suggestion: You could catch the ten o’clock bus tomorrow.
Possibility: I could pick you up from soccer practice.
Might is used for possibility
Possibility: I might travel to Asia next year.
Ought to used for advice
Advice: You ought to check the papers for job listings
Shall used for suggestion
Suggestion: We shall see what happens.
Will used for prediction, promise, habits, affirmation, request
Prediction: I think the fundraiser will be very successful.
Promise: I will be there at 7 o’clock on the dot.
Affirmation: “Drive carefully” “I will!”
Request: Will you join my for lunch this afternoon?